This invention relates to a device for generating a light beam with three or more sectors for a visual glide angle indicator for aircraft and a visual guide angle indicator comprising the device.
More specifically, this invention relates to an optical device which is able to project a beam of light forming a luminous path for guiding the aircraft, preferably helicopters, during landing, both on the ground and on fixed or floating marine platforms.
In the technical sector for aircraft guidance signalling, there are prior art luminous devices designed to indicate a predetermined guide angle to helicopters and aircraft, to allow the helicopters and aircraft to perform a correct manoeuvre for approaching the landing surface. In these applications, the light beam must be oriented both in azimuth and altitude so as to identify the desired landing path. In the applications on floating platforms, for example naval units, the light beam must also be stabilised relative to the movements of the platform induced by the wave motion of the sea. The stabilisation is performed relative to the rotary movements about the two axes: rolling, longitudinal to the axis of the platform, and pitching, at right angles to the axis of the platform.
The prior art devices have a light source, designed to produce a light beam which is transmitted by a suitable unit for creating the image.
Subsequently, the luminous image created is projected by an optical lens and directed in the predetermined direction, using a reflective element such as a suitably oriented mirror.
It should be noted that the projected image has a plurality of luminous sectors (more specifically, three) of different colours for guiding and providing a reference to the pilot during approach to the aircraft landing pad.
Currently, patent EP1547922, by the same Applicant, discloses a solution for the coupling of a LED light source with an optical fibre optical guide for forming an image to be projected. That solution, whilst it is technically valid, implies the need for an optical system comprising a sequence of collector lenses on the individual LED-optical fibre couplings, which are of special construction and expensive.
Alternatively, there is a prior art solution wherein the image is made using luminous devices creating luminous surfaces, the making of which is however currently difficult due to the unavailability on the market of panels with an adequate output.
However, patent EP2261122 proposes a solution diametrically opposite those just described. In effect, this solution provides for the use of a laser light source with a system for making the luminous sectors which is completely different from the previous solutions.
Disadvantageously, the use of the laser raises problems regarding its flexibility, as well as regarding the colours of the light beam. Moreover, the high speed, high precision pointing of the beam also raises a non-insignificant technical problem.
It is to be noted that, as disclosed in EP2495169, also in the neighbouring field of the production of Precision Approach Path Indicator (PAPI) it is known a solution which implies use of transparent solid blocks as guide for the light path. However, such a solution is similar to the one of EP2261122 and has the same disadvantages.